Scaling is the accumulation of unwanted material on solid surfaces to the detriment of the function. The scaling material can consist of either living organisms are non-living substances, organic or inorganic. Scaling is a common and diverse phenomenon. Scaling can occur on the ship hulls, scaling of heat transfer components throughout process industries, and deposits found on a variety of other structures.
When scaling occurs on heat exchange surfaces, it tends to reduce the thermal efficiency, decrease the heat flux, increases temperature on the hot side, decreases temperature on the cold side, induces under-deposit corrosion, and increases the use of cooling water. In piping and flow channels, the scaling will reduce flow, increase pressure drop, increase upstream pressure, increase energy expenditure, cause float oscillations and cavitation, and also induce vibrations and cause float blockage. When scaling occurs on ship hulls, it can create additional drag, increased fuel usage and reduce maximum speed. Scaling on turbines will reduce the efficiency and increase the probability of failure. In the case of reverse osmosis membranes, such scaling will increase pressure drop, increase energy expenditure, reduce flux, and will eventually cause membrane failure. Scaling can also incur on injection/spray nozzles. As a result, this can cause an incorrect amount of injected fluid, a malformed jet, component inefficiency and component failure. Whenever scaling occurs in the production zone of petroleum reservoirs and oil wells, this can result in decreased petroleum production, plugging, and an actual stoppage of flow. Whenever these issues occur, in order to properly descale the particular item, a shutdown of the facilities is often required. The shutdown can reduce production time and increase costs.
The result of scaling is ubiquitous and generates tremendous operational losses. For example, one estimate puts the losses due scaling of heat exchangers in industrialized nations to be approximately 0.25% of the gross domestic product. The losses initially result from impaired heat transfer, corrosion damage, increase pressure drop, flow blockages, flow free distribution inside components, flow instabilities, induced vibrations, fretting, and a large number of other unanticipated problems. Additionally, there are significant ecological costs associated with such scaling.
Typically, biosides can be applied so as to reduce scaling. These biosides can include inorganic chlorine and bromide compounds, chlorine and bromide cleavers, ozone oxygen cleavers, and unoxidizable biosides. One of the most important unoxidizable biosides is a mixture of chloromethyl-isothiazolinone and methyl-isothiazolinone. Chemical scaling inhibitors can reduce scaling in many systems by interfering with the crystallization, attachment or consolidation steps of the scaling process. These can include chelating agents, long-chain aliphatic ammines or polyamines, organic phosphonic acids, polyelectrolytes, and polymethacrylic acid. In the case of boilers, aluminum or magnesium additives can serve to avoid such scaling. Unfortunately, each of these components can often be toxic to the environment and can require the persons applying the descaling agents to wear specialized equipment to prevent exposure to such toxic chemicals.
Chemical or mechanical cleaning processes for the removal of deposits and scales are used when the scaling reaches the point of impacting the performance of the system. These processes comprise pickling with acids and complexing agents, cleaning with pipe-velocity water jets, recirculating or blasting with metal, or propelling off-line mechanical bullet-type tube cleaners. The chemical cleaning causes environmental problems through handling, application, storage and disposal of chemicals. The mechanical cleaning can be an environmentally friendlier solution though often requires a great deal of time, equipment and costs. As such, a need has developed so as to provide a descaling solution that can be applied which is non-toxic, extremely effective, and reduces facility downtime.
In the past, various patents have issued relating to descaling compositions. For example, U.S. Pat. No. 2,450,861, issued on Oct. 5, 1948 to H. A. Robinson, describes a composition for descaling ferrous metal. This composition includes 5 to 25% by weight of hydrogen chloride, 0.1 to 1% of an organic nitrogen base, and 2.2 to 3.3% of a water-soluble salt. The salt can be a water-soluble divalent chromium salt, or a titanium salt.
U.S. Pat. No. 2,485,528, issued on Oct. 18, 1949 to Cardwell et al., shows another composition for descaling ferrous metal surfaces. This composition includes an aqueous solution containing from 5 to 25% of hydrogen chloride, and between 0.1 and 1% of an organic nitrogen base soluble in the hydrochloric acid. The organic nitrogen base can be either an aromatic or heterocyclic nitrogen base. The composition also includes from 0.1 to 2% of the water-soluble thiocyanate.
U.S. Pat. No. 3,025,225, issued on Mar. 13, 1962 to Snyder et al., discloses an electrolytic acid for the descaling of metals. This descaling composition is in a bath that include 60% to 95% of sulfuric acid, 0.5% to 20% of hydrofluoric acid, 0.001% of sulfite ions, 0 to 0.5% of orthophosphoric acid, and the remainder being water.
U.S. Pat. No. 3,030,239, issued on Apr. 17, 1962 to Mekjeam et al., teaches a process for the descaling of metals. The metal to be treated receives between 50 to 90% of an alkali metal hydroxide, 2 to 25% of an alkali metal phosphate, 0.5% to 30% of an alkali metal carbonate, and 0.5 to 25% of a material selected from the group of alkali metal halide, alkaline earth metal halides, and mixtures thereof.
U.S. Pat. No. 3,121,026, issued on Feb. 11, 1964 to Beigay, discloses the descaling of metals and alloys with aqueous potassium hydroxide. The process is intended to remove metal oxide scale on a surface thereof. The article is brought into contact with an aqueous bath that contains 60 to 90% potassium chloride oxide and at least 10% water while maintaining the bath at a temperature between 300° F. to 450° F.
U.S. Pat. No. 3,277,008, issued on Oct. 4, 1966 to A. H. Heit, discloses a surface cleaning method and composition. In particular, this composition serves to descale internal metal surfaces of a jacket of glass-lined jacketed equipment while preventing spallation of the glass lining. An aqueous acid solution contains between 2 and 20% of an alpha-beta ethylenically unsaturated, water-soluble carboxylic acid. The carboxylic gas serves to react with insoluble phosphates, carbonates, and hydroxide to produce water-soluble compounds.
U.S. Pat. No. 4,439,339, issued on Mar. 27, 1984 to C. J. Doumit, provides a descaler composition and method for the removal of scale from freshwater production equipment such as desalinators or evaporators, along with distillation units, heat exchangers and boilers. The composition includes a blend of acids of various strengths so as to provide a timed release effect. The acids include hydrochloric acid, dichloroacetic acid, and acetic acid. The composition further contains a surfactant, such as isopropyl alcohol, which reacts with the acids. The composition further includes an acid-based indicator to signify neutralization of the acidizer during scale removal.
U.S. Pat. No. 5,575,857, issued on Nov. 19, 1996 to Lunski et al., provides an aqueous alkaline metal descaling concentrate. This process includes the steps of applying an aqueous solution containing alkali metal carbonate salts and a hydrotrope so as to remove organic scale. Additionally, the composition further includes a mixture of potassium and sodium carbonate salts.
It is an object of the present invention to provide a method for forming a descaling composition which can be utilized for the descaling of process equipment and processing towers.
It is another object of the present invention to provide a process for forming a descaling composition that serves to remove encrustions, such as metal oxidizations, encrusted salts, silica, and carbonates.
It is another object of the present invention to provide a process that can remove those encrustation that are generated in the processing of oil and gas.
It is a further object of the present invention to provide a process that can effectively clean heat exchangers.
It is another object of the present invention to provide a process for forming a descaling composition in which the descaling composition is a stainless steel passivator.
It is another object of the present invention to provide a process for forming a descaling composition in which the descaling composition will not damage seals, paints, gaskets and thermal insulation.
It is further object of the present invention provide a process for the forming of a descaling composition in which the descaling composition will not degrade the material upon which it is applied.
It is another object of the present invention to provide a process for the formation of a descaling composition in which the descaling composition is biodegradable, is colorless, has minimal odor, is non-corrosive, is non-toxic, and is nonflammable.
It is another object of the present invention provide a process for the forming of a descaling composition in which the descaling composition can extend the life of the equipment to which it is applied.
It is another object of the present invention provide a process for the formation of a descaling composition in which the descaling composition is operator-friendly.
It is a further object of the present invention to provide a process for the forming of a descaling composition in which the descaling composition is reusable.
It is another object of the present invention to provide a process for the formation of a descaling composition which serves to reduce plant downtime.
It is still a further object of the present invention to provide a process for the formation of a descaling composition which serves to increase equipment productivity.
It is still another object of the present invention to provide a process for the formation of a descaling composition in which the descaling composition will serve to reduce maintenance costs.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.